Background: Oxidative stress has been implicated in the cardiovascular complications that affect hemodialysis (HD) patients. Ethylene-vinyl alcohol copolymer (EVAL) dialyzer membrane induces less production of reactive oxygen species as compared to conventional dialyzers. We evaluated the impact of EVAL membrane on plasma protein oxidation in HD patients. Methods: HD patients treated with cellulose triacetate (CTA) dialyzers were selected. In the first study performed in a 2-month crossover design alternating between CTA and EVAL, nonmercaptalbumin and advanced oxidation protein products levels were measured in the predialysis blood from 10 subjects. In the second study, predialysis plasma myeloperoxidase levels were measured before and after a 2-week EVAL treatment on 12 patients. Results: Plasma advanced oxidation protein products levels were reduced after a 2-month EVAL treatment and increased again after CTA treatment, although the nonmercaptalbumin proportions were not affected significantly by the change in dialyzer membranes. The following study, a 2-week EVAL treatment, showed the decrease in myeloperoxidase levels immediately before HD. Conclusion: The frequent use of EVAL dialyzers has been shown to reduce protein oxidation, possibly through the suppression of circulating phagocytes. This novel biocompatible dialyzer is expected to protect cardiovascular mortality in HD patients.